The pivot joint in hand tools receives large shear loads as force is applied to the workpiece during use. In cutting tools, for example, scissors, shears, and snips, the pivot joints are also subject to axial loads tending to separate the cutting blades as the blades are forced through the work material. The ride of the blades, that is, the force holding the blades against one another, is typically set at the factory during assembly of the tool. This presents certain disadvantages, however. The factory set ride is not generally suitable for every user of the tool. In addition, wear on the blades or the thickness of the material being cut may require user adjustment of the ride. Further, for cleaning or sharpening, the user will need to disassemble the blades. Conventional fastener arrangements usually require the use of a screwdriver and/or pliers, for adjustment and disassembly, which is cumbersome and time consuming.
The invention provides a fastener for pivoting hand tools, in particular for cutting tools, that allows simple adjustment of the fastening tension, so that the user can easily adjust the ride.
The invention also provides a fastener that allows quick release of the tool elements for disassembly, without the use of tools.
The fastener according to the invention provides a pivot bearing that improves on convention pivot bearings, usually the bolt connector itself, for more reliable and smoother operation of the tool.
According to the invention, a pivot fastener includes bushings that are press fit into mounting holes in the pivoting tool elements. The bushings and the mounting holes are shaped to resist relative rotation, for example, by keying the mounting holes and forming mating flats on the bushings, or by using a square hole and square-profiled bushing. A bolt inserted through holes in the bushings and secured by a thumb nut fastens the arrangement together.
According to the invention, a first bushing has a relatively wide hole that accepts the shank of the second bushing. The contacting surfaces of the bushings provides a pivot bearing when the tool elements are pivoted.
According to another aspect of the invention, a first bushing has a cap with a recess. A slotted opening in the recess connects to the through hole. The bolt is inserted through the through hole with the head disposed in the recess. The bottom of the recess includes shoulders that define the slotted opening and provide bearing surfaces for the bolt head. Within the normal pivoting range of the tool elements, the bolt head bears on the shoulders to keep the tool elements fastened. By pivoting the tool elements past the normal range, the bolt head, which is shaped to correspond to the slotted opening, is aligned with the opening and can pass through the first bushing. The tool elements are thereby released for disassembling the tool.
According to another aspect of the invention, the second bushing includes a flange that bears on the second tool element. The bolt extends through the second bushing, and a nut is screwed onto the bolt, applying tension across the fastener. The nut can be turned to adjust the tension, and accordingly, the ride on the blades. The nut is provided with ribs or wings to allow hand turning.